1. Field of the Invention
The present invention relates to a cleaning blade for an electrophotographic apparatus used to remove a remaining toner on image bearing members such as a photoreceptor drum, a transfer belt, and an intermediate transfer member, which are used in an electrophotographic apparatus.
2. Description of the Related Art
In an electrophotographic apparatus, a variety of cleaning blades are disposed in order to remove a remaining toner on image bearing members such as a photoreceptor drum, a transfer belt, and an intermediate transfer member. Blade members of these cleaning blades are mainly formed with a thermosetting polyurethane elastomer from the viewpoint of plastic deformation and resistance to wear.
Recently, a demand for high quality images has been increased, leading to a more spherical form of a toner with a smaller particle size. For this reason, higher cleaning performance has been demanded of the cleaning blade, and better contact of the cleaning blade with the image bearing member has been examined in order to ensure such cleaning performance.
Unfortunately, a larger contact pressure increases the friction between the blade member and the image bearing member. For this reason, the drive torque of the image bearing member is increased, and the blade member may be turned over. Accordingly, in order to reduce the drive torque of the image bearing member, reduction in the friction with the blade member, namely, production of the blade member having smaller friction is considered.
As a method for solving the problems concerning the cleaning blade formed with a thermosetting polyurethane elastomer, techniques (1) to (3) below are known.
(1) The hardness of the entire thermosetting polyurethane elastomer is increased to reduce friction.
(2) A laminate structure with high hardness is provided in an edge portion of the blade member to contact the image bearing member (Japanese Patent Application Laid-Open No. 2008-268494).
(3) A polyurethane resin as a base material for the blade member is reacted with an isocyanate compound to provide a cured layer in the contact region of the blade member to contact the image bearing member (Japanese Patent Application Laid-Open No. 2007-078987).
Unfortunately, the methods above have problems described below.
In the method (1), if the hardness of the entire blade member is high, the image bearing member is easily worn out or damaged.
In the method (2), two materials having different properties are layered. For this reason, the behaviors of the two materials when the blade contacts the image bearing member are different, and no stable contact state can be obtained.
In the method (3), the blade member is produced as follows: a polyurethane resin as a base material for the blade member is impregnated with an isocyanate compound, and the remaining isocyanate compound on the surface is removed. However, if the friction of the contact region of the blade member to contact the image bearing member is reduced to a necessary level, namely, if the hardness of the contact region of the blade member is increased, a wider range within the contact region is unintendedly impregnated with the isocyanate compound to increase the hardness of the contact region. As a result, a region short of rubber elasticity is increased, and cleaning properties are reduced.